Altered kinetic strategy for the control of swing limb elevation over obstacles in unilateral below-knee amputee gait

Our goal was to document the kinetic strategies for obstacle avoidance in b elow-knee amputees. Kinematic data were collected as unilateral below-knee traumatic amputees stepped over obstacles of various heights in the walking path. Inverse dynamics were employed to calculate power profiles and work during the limb-elevation and limb-lowering phases. Limb elevation was achi eved by employing a different strategy of intra-limb interaction for elevat ion of the prosthetic limb than for the sound limb, which was similar to th at seen in healthy adult non-amputees. As obstacle height increased, prosth etic side knee flexion was increased by modulating the work done at the hip , and not the knee, as seen on the sound side. Although the strength of the muscles about the residual knee was preserved, the range of motion of that knee had previously been found to be somewhat limited. Perhaps more import antly, potential instability of the interface between the stump and the pro sthetic socket, and associated discomfort at the stump could explain the al tered limb-elevation strategy. Interestingly, the limb-lowering strategy se en in the sound limb and in non-amputees already features modulation of rot ational and translational work at the hip: so an alternate strategy was not required. Thus, following a major insult to the sensory and neuromuscular system, the CNS is able to update the internal model of the locomotor appar atus as the individual uses the new limb in a variety of movements, and mod ify control strategies as appropriate. (C) 1999 Elsevier Science Ltd. All r ights reserved.